Occlusive and adhesive wound dressings are well known in which the adhesive material takes the form of a pliant water-absorbing, hydrocolloid-containing "barrier" material having both wet and dry tack. The outer surface of the barrier layer is usually covered by a thin backing layer of polymeric film or foam which is preferably highly stretchable so that the backing layer may expand to accommodate the increased volume of the dressing's barrier layer as it absorbs exudate from a wound site. Reference may be had to U.S. Pat. Nos. 4,738,257, 4,477,325, and 4,231,369 for details of wound dressings embodying such features.
The skin-contacting surface of such a barrier layer is normally maintained in clean and sterile condition until application by means of one or more release sheets. Such sheets are commonly formed of siliconized paper and, to facilitate their removal from the barrier layer, are frequently arranged in pairs meeting along one or more lines of separation extending across the dressing. A user simply peels away the release sheets along each line of separation, thereby exposing the barrier surface for application to the wound area.
One disadvantage of such a construction is that the barrier material may be exposed, dry out, and lose its dry tack along the line of separation, even during relatively short periods of storage. Also, the more liquid or semi-liquid constituents of the barrier material (e.g., polyisobutylene) may tend to bleed through the release sheet along the line of separation and, at the very least, cause an unsightly discoloration of the release sheet along that line. Even if the edges of the sheets are carefully positioned so that they are disposed in abuting contact at the time of manufacture, the soft pliant character of the barrier material, and its characteristic ability to swell in the presence of moisture because of its hydrocolloid content, may result in separation of the edges during an interval prior to use. Furthermore, locating the edges in contiguous or abuting relation renders the seam practically invisible, thereby making separation and removal of the release sheets all the more difficult. Thus, if it is possible to maintain the opposing edges of the release sheets in abuting relation prior to use, the removal of those sheets is rendered more difficult and, on the other hand, if such edges are spaced apart during manufacture, or become spaced apart during storage, drying, discoloration and degradation of the barrier material and of the edges of the release sheet may result.
It is therefore an important aspect of this invention to provide a hydrocolloid-type occlusive dressing for the care of skin wounds in which the barrier layer is protected by release sheet means composed of at least two sections meeting along a line of separation. That line is defined by a series of alternating slits and connecting segments. The integral connecting segments join the two sections together and maintain opposing edges of the slits in abuting or contiguous relation until the release sheet sections are removed, at which time the connecting segments become torn or ruptured. Until the segments are so torn, the release sheet sections remain connected and prevent the skin barrier material from drying, discoloring, degrading, and bleeding outwardly along the line of separation.
The sizes of the slits and connecting segments are important because the purpose of the connecting segments is to keep the edges of the release sheet sections in closed condition, despite the pliant character of the adhesive barrier material over which the release sheet sections extend, while at the same time allowing the sections to be peeled away from the barrier layer and away from each other as easily as if such connecting segments were not present. In general, it has been found that the slits should each have a length within the range of about 5 to 25 mm and the connecting segments should each be of a length within the range of about 0.1 to 1.0 mm. Preferred ranges are 6 to 16 mm and 0.3 to 0.7 mm, respectively. When such dimensions are embodied in a paper release sheet covering a pliant barrier layer, it has been found that the connecting segments may be easily torn apart as the release sheet sections are peeled from the barrier layer but, until the time of release sheet removal, the dimensions and spacing of the segments should effectively maintain the slits in closed condition.
Since the slits are normally maintained in closed condition, the actual line of intended separation may not be readily visible to a user. However, at least one of the release sheet sections is provided with a visible locator stripe alongside the line of separation, thereby revealing the location of the line to a user preparing to peel the release sheet sections away from the barrier layer and, as part of the process, to tear or rupture the connecting segments that have maintained the edges of the slits in closed condition.
In manufacture of the product, the release sheet should be slitted and imprinted before being applied to the adhesive surface of the barrier layer. The slitting should constitute a clean cutting operation which forms sharply-cut edges for the slits without displacing or dislodging any appreciable amount of material from the sheet, so that the flexibility of the sheet, which is formed of paper or other easily-tearable material, helps insure that the edges of the slit flex towards an abuting relation after the sheet has advanced past the cutting blade. During the next step in which the slitted and imprinted sheet is applied to the surface of the barrier layer, it is believed that the soft, pliant character of the barrier layer contributes in urging the edges into contiguous relation should such edges have become slightly separated or misaligned following the slitting operation.
Other features, advantages, and objects of the invention will become apparent from the specification and drawings.